/*
 * Sample disk driver, from the beginning.
 * Ported to kernel v2.6.31 by casualfish. 2010.7.20
 */

//#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>

#include <linux/sched.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h>   /* kmalloc() */
#include <linux/fs.h>   /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/timer.h>
#include <linux/types.h> /* size_t */
#include <linux/fcntl.h> /* O_ACCMODE */
#include <linux/hdreg.h> /* HDIO_GETGEO */
#include <linux/kdev_t.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h> /* invalidate_bdev */
#include <linux/bio.h>

MODULE_LICENSE("Dual BSD/GPL");

static int sbull_major = 0;
module_param(sbull_major, int, 0);
static int hardsect_size = 512;
module_param(hardsect_size, int, 0);
static int nsectors = 1024; /* How big the drive is */
module_param(nsectors, int, 0);
static int ndevices = 4;
module_param(ndevices, int, 0);

/*
 * The different "request modes" we can use.
 */
enum {
    RM_SIMPLE = 0, /* The extra-simple request function */
    RM_FULL    = 1, /* The full-blown version */
    RM_NOQUEUE = 2, /* Use make_request */
};
static int request_mode = RM_SIMPLE;
module_param(request_mode, int, 0);

/*
 * Minor number and partition management.
 */
#define SBULL_MINORS 16
#define MINOR_SHIFT 4                   // 支持4个设备
#define DEVNUM(kdevnum) (MINOR(kdev_t_to_nr(kdevnum)) >> MINOR_SHIFT

        /*
         * We can tweak our hardware sector size, but the kernel talks to us
         * in terms of small sectors, always.
         */
#define KERNEL_SECTOR_SIZE 512

        /*
         * After this much idle time, the driver will simulate a media change.
         */
#define INVALIDATE_DELAY 30*HZ

        /*
         * The internal representation of our device.
         */
        struct sbull_dev {
        int size;                       /* Device size in sectors */
        u8 *data;                       /* The data array */
        short users;                    /* How many users */
        short media_change;             /* Flag a media change? */
        spinlock_t lock;                /* For mutual exclusion */
        struct request_queue *queue;    /* The device request queue */
        struct gendisk *gd;             /* The gendisk structure */
        struct timer_list timer;        /* For simulated media changes */
        };

static struct sbull_dev *Devices = NULL;

/*
 * Handle an I/O request, in sectors.
 */
static void sbull_transfer(struct sbull_dev *dev, unsigned long sector,
        unsigned long nsect, char *buffer, int write)
{
    unsigned long offset = sector*KERNEL_SECTOR_SIZE;
    unsigned long nbytes = nsect*KERNEL_SECTOR_SIZE;

    if ((offset + nbytes) > dev->size) {
        printk (KERN_NOTICE "Beyond-end write (%ld %ld)\n", offset, nbytes);
        return;
    }
    if (write)
        memcpy(dev->data + offset, buffer, nbytes);
    else
        memcpy(buffer, dev->data + offset, nbytes);
}

/*
 * The simple form of the request function.
 */
static void sbull_request(struct request_queue *q)
{
    struct request *req;

    req = blk_fetch_request(q);
    while (req != NULL) {
        struct sbull_dev *dev = req->rq_disk->private_data;
        if (! blk_fs_request(req)) {
            printk (KERN_NOTICE "Skip non-fs request\n");
            __blk_end_request_all(req, -EIO);
            continue;
        }
        //    printk (KERN_NOTICE "Req dev %d dir %ld sec %ld, nr %d f %lx\n",
        //        dev - Devices, rq_data_dir(req),
        //        req->sector, req->current_nr_sectors,
        //        req->flags);
        sbull_transfer(dev, blk_rq_pos(req), blk_rq_cur_sectors(req), req->buffer, rq_data_dir(req));
        /* end_request(req, 1); */
        if(!__blk_end_request_cur(req, 0)) {
            req = blk_fetch_request(q);
        }
    }
}


/*
 * Transfer a single BIO.
 */
static int sbull_xfer_bio(struct sbull_dev *dev, struct bio *bio)
{
    int i;
    struct bio_vec *bvec;
    sector_t sector = bio->bi_sector;

    /* Do each segment independently. */
    bio_for_each_segment(bvec, bio, i) {
        char *buffer = __bio_kmap_atomic(bio, i, KM_USER0);
        sbull_transfer(dev, sector, bio_cur_bytes(bio)>>9 /* in sectors */, 
                buffer, bio_data_dir(bio) == WRITE);
        sector += bio_cur_bytes(bio)>>9; /* in sectors */
        __bio_kunmap_atomic(bio, KM_USER0);
    }
    return 0; /* Always "succeed" */
}

/*
 * Transfer a full request.
 */
static int sbull_xfer_request(struct sbull_dev *dev, struct request *req)
{
    struct bio *bio;
    int nsect = 0;

    __rq_for_each_bio(bio, req) {
        sbull_xfer_bio(dev, bio);
        nsect += bio->bi_size/KERNEL_SECTOR_SIZE;
    }
    return nsect;
}

/*
 * Smarter request function that "handles clustering".
 */
static void sbull_full_request(struct request_queue *q)
{
    struct request *req;
    int sectors_xferred;
    struct sbull_dev *dev = q->queuedata;

    req = blk_fetch_request(q);
    while (req != NULL) {
        if (! blk_fs_request(req)) {
            printk (KERN_NOTICE "Skip non-fs request\n");
            __blk_end_request_all(req, -EIO);
            continue;
        }
        sectors_xferred = sbull_xfer_request(dev, req);
        if (!__blk_end_request_cur(req, 0)) {
            blk_fetch_request(q);
        }
    }
}

/*
 * The direct make request version.
 */
static int sbull_make_request(struct request_queue *q, struct bio *bio)
{
    struct sbull_dev *dev = q->queuedata;
    int status;

    status = sbull_xfer_bio(dev, bio);
    bio_endio(bio, status);
    return 0;
}


/*
 * Open and close.
 */

static int sbull_open(struct block_device *device, fmode_t mode)
{
    struct sbull_dev *dev = device->bd_disk->private_data;

    del_timer_sync(&dev->timer);
    /* filp->private_data = dev;*/
    spin_lock(&dev->lock);
    if (! dev->users) 
        check_disk_change(device);
    dev->users++;
    spin_unlock(&dev->lock);
    return 0;
}

static int sbull_release(struct gendisk *disk, fmode_t mode)
{
    struct sbull_dev *dev = disk->private_data;

    spin_lock(&dev->lock);
    dev->users--;

    if (!dev->users) {
        dev->timer.expires = jiffies + INVALIDATE_DELAY;
        add_timer(&dev->timer);
    }
    spin_unlock(&dev->lock);

    return 0;
}

/*
 * Look for a (simulated) media change.
 */
int sbull_media_changed(struct gendisk *gd)
{
    struct sbull_dev *dev = gd->private_data;

    return dev->media_change;
}

/*
 * Revalidate. WE DO NOT TAKE THE LOCK HERE, for fear of deadlocking
 * with open. That needs to be reevaluated.
 */
int sbull_revalidate(struct gendisk *gd)
{
    struct sbull_dev *dev = gd->private_data;

    if (dev->media_change) {
        dev->media_change = 0;
        memset (dev->data, 0, dev->size);
    }
    return 0;
}

/*
 * The "invalidate" function runs out of the device timer; it sets
 * a flag to simulate the removal of the media.
 */
void sbull_invalidate(unsigned long ldev)
{
    struct sbull_dev *dev = (struct sbull_dev *) ldev;

    spin_lock(&dev->lock);
    if (dev->users || !dev->data) 
        printk (KERN_WARNING "sbull: timer sanity check failed\n");
    else
        dev->media_change = 1;
    spin_unlock(&dev->lock);
}

/*
 * The ioctl() implementation
 */

int sbull_ioctl (struct block_device *device, fmode_t mode,
        unsigned int cmd, unsigned long arg)
{
    long size;
    struct hd_geometry geo;
    struct sbull_dev *dev = device->bd_disk->private_data;

    switch(cmd) {
        case HDIO_GETGEO:
            /*
             * Get geometry: since we are a virtual device, we have to make
             * up something plausible. So we claim 16 sectors, four heads,
             * and calculate the corresponding number of cylinders. We set the
             * start of data at sector four.
             */
            size = dev->size*(hardsect_size/KERNEL_SECTOR_SIZE);
            geo.cylinders = (size & ~0x3f) >> 6;
            geo.heads = 4;
            geo.sectors = 16;
            geo.start = 4;
            if (copy_to_user((void __user *) arg, &geo, sizeof(geo)))
                return -EFAULT;
            return 0;
    }

    return -ENOTTY; /* unknown command */
}

/*
 * The device operations structure.
 */
static struct block_device_operations sbull_ops = {
    .owner           = THIS_MODULE,
    .open           = sbull_open,
    .release = sbull_release,
    .media_changed   = sbull_media_changed,
    .revalidate_disk = sbull_revalidate,
    .ioctl          = sbull_ioctl
};


/*
 * Set up our internal device.
 */
static void setup_device(struct sbull_dev *dev, int which)
{
    /*
     * Get some memory.
     */
    memset (dev, 0, sizeof (struct sbull_dev));
    dev->size = nsectors*hardsect_size;
    dev->data = vmalloc(dev->size);
    if (dev->data == NULL) {
        printk (KERN_NOTICE "vmalloc failure.\n");
        return;
    }
    spin_lock_init(&dev->lock);

    /*
     * The timer which "invalidates" the device.
     */
    init_timer(&dev->timer);
    dev->timer.data = (unsigned long) dev;
    dev->timer.function = sbull_invalidate;

    /*
     * The I/O queue, depending on whether we are using our own
     * make_request function or not.
     */
    switch (request_mode) {
        case RM_NOQUEUE:
            dev->queue = blk_alloc_queue(GFP_KERNEL);
            if (dev->queue == NULL)
                goto out_vfree;
            blk_queue_make_request(dev->queue, sbull_make_request);
            break;

        case RM_FULL:
            dev->queue = blk_init_queue(sbull_full_request, &dev->lock);
            if (dev->queue == NULL)
                goto out_vfree;
            break;

        default:
            printk(KERN_NOTICE "Bad request mode %d, using simple\n", request_mode);
            /* fall into.. */

        case RM_SIMPLE:
            dev->queue = blk_init_queue(sbull_request, &dev->lock);
            if (dev->queue == NULL)
                goto out_vfree;
            break;
    }
    blk_queue_logical_block_size(dev->queue, hardsect_size);
    dev->queue->queuedata = dev;
    /*
     * And the gendisk structure.
     */
    dev->gd = alloc_disk(SBULL_MINORS);
    if (! dev->gd) {
        printk (KERN_NOTICE "alloc_disk failure\n");
        goto out_vfree;
    }
    dev->gd->major = sbull_major;
    dev->gd->first_minor = which*SBULL_MINORS;
    dev->gd->fops = &sbull_ops;
    dev->gd->queue = dev->queue;
    dev->gd->private_data = dev;
    snprintf (dev->gd->disk_name, 32, "sbull%c", which + 'a');
    set_capacity(dev->gd, nsectors*(hardsect_size/KERNEL_SECTOR_SIZE));
    add_disk(dev->gd);
    return;

out_vfree:
    if (dev->data)
        vfree(dev->data);
}

static int __init sbull_init(void)
{
    int i;
    /*
     * Get registered.
     */
    sbull_major = register_blkdev(sbull_major, "sbull");
    if (sbull_major <= 0) {
        printk(KERN_WARNING "sbull: unable to get major number\n");
        return -EBUSY;
    }
    /*
     * Allocate the device array, and initialize each one.
     */
    Devices = kmalloc(ndevices*sizeof (struct sbull_dev), GFP_KERNEL);
    if (Devices == NULL)
        goto out_unregister;
    for (i = 0; i < ndevices; i++) 
        setup_device(Devices + i, i);

    return 0;

out_unregister:
    unregister_blkdev(sbull_major, "sbd");
    return -ENOMEM;
}

static void sbull_exit(void)
{
    int i;

    for (i = 0; i < ndevices; i++) {
        struct sbull_dev *dev = Devices + i;

        del_timer_sync(&dev->timer);
        if (dev->gd) {
            del_gendisk(dev->gd);
            put_disk(dev->gd);
        }
        if (dev->queue)
            blk_cleanup_queue(dev->queue);
        if (dev->data)
            vfree(dev->data);
    }
    unregister_blkdev(sbull_major, "sbull");
    kfree(Devices);
}

module_init(sbull_init);
module_exit(sbull_exit);
